"That does not go with our vocation and mission – such temptation should be far from us," it said.

If a priest did want to study at a secular university, he would need a letter of approval from his bishop, the letter added, and the Episcopal Conference would seek to find a similar course at an ecclesiastical college.

The bishops said that this ban on secular study was inspired by Pope Francis' homily on 26 April last year, when he ordained 19 new priests.

In the homily, Francis encouraged priests to "diligently read and meditate on the Word of the Lord, that you may believe what you read, teach what you have learned in faith, and practice what you teach."

El Salvador is a majority-Christian country, with 47 per cent of the nation identifying with as Roman Catholic.